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  • Classes to Entities; Like-class inheritence problems

    - by Stacey
    Beyond work, some friends and I are trying to build a game of sorts; The way we structure some of it works pretty well for a normal object oriented approach, but as most developers will attest this does not always translate itself well into a database persistent approach. This is not the absolute layout of what we have, it is just a sample model given for sake of representation. The whole project is being done in C# 4.0, and we have every intention of using Entity Framework 4.0 (unless Fluent nHibernate can really offer us something we outright cannot do in EF). One of the problems we keep running across is inheriting things in database models. Using the Entity Framework designer, I can draw the same code I have below; but I'm sure it is pretty obvious that it doesn't work like it is expected to. To clarify a little bit; 'Items' have bonuses, which can be of anything. Therefore, every part of the game must derive from something similar so that no matter what is 'changed' it is all at a basic enough level to be hooked into. Sounds fairly simple and straightforward, right? So then, we inherit everything that pertains to the game from 'Unit'. Weights, Measures, Random (think like dice, maybe?), and there will be other such entities. Some of them are similar, but in code they will each react differently. We're having a really big problem with abstracting this kind of thing into a database model. Without 'Enum' support, it is proving difficult to translate into multiple tables that still share a common listing. One solution we've depicted is to use a 'key ring' type approach, where everything that attaches to a character is stored on a 'Ring' with a 'Key', where each Key has a Value that represents a type. This works functionally but we've discovered it becomes very sluggish and performs poorly. We also dislike this approach because it begins to feel as if everything is 'dumped' into one class; which makes management and logical structure difficult to adhere to. I was hoping someone else might have some ideas on what I could do with this problem. It's really driving me up the wall; To summarize; the goal is to build a type (Unit) that can be used as a base type (Table per Type) for generic reference across a relatively global scope, without having to dump everything into a single collection. I can use an Interface to determine actual behavior so that isn't too big of an issue. This is 'roughly' the same idea expressed in the Entity Framework.

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  • Android: Creating custom class of resources

    - by Sebastian
    Hi, R class on android has it's limitations. You can't use the resources dynamically for loading audio, pictures or whatever. If you wan't for example, load a set of audio files for a choosen object you can't do something like: R.raw."string-upon-choosen-object" I'm new to android and at least I didn't find how you could do that, depending on what objects are choosen or something more dynamic than that. So, I thought about making it dynamic with a little of memory overhead. But, I'm in doubt if it's worth it or just working different with external resources. The idea is this: Modify the ant build xml to execute my own task. This task, is a java program that parses the R.java file building a set of HashMaps with it's pair (key, value). I have done this manually and It's working good. So I need some experts voice about it. This is how I will manage the whole thing: Generate a base Application class, e.g. MainApplicationResources that builds up all the require methods and attributes. Then, you can access those methods invoking getApplication() and then the desired method. Something like this: package [packageName] import android.app.Application; import java.util.HashMap; public class MainActivityResources extends Application { private HashMap<String,Integer> [resNameObj1]; private HashMap<String,Integer> [resNameObj2]; ... private HashMap<String,Integer> [resNameObjN]; public MainActivityResources() { super(); [resNameObj1] = new HashMap<String,Integer>(); [resNameObj1].put("[resNameObj1_Key1]", new Integer([resNameObj1_Value1])); [resNameObj1].put("[resNameObj1_Key2]", new Integer([resNameObj1_Value2])); [resNameObj2] = new HashMap<String,Integer>(); [resNameObj2].put("[resNameObj2_Key1]", new Integer([resNameObj2_Value1])); [resNameObj2].put("[resNameObj2_Key2]", new Integer([resNameObj2_Value2])); ... [resNameObjN] = new HashMap<String,Integer>(); [resNameObjN].put("[resNameObjN_Key1]", new Integer([resNameObjN_Value1])); [resNameObjN].put("[resNameObjN_Key2]", new Integer([resNameObjN_Value2])); } public int get[ResNameObj1](String resourceName) { return [resNameObj1].get(resourceName).intValue(); } public int get[ResNameObj2](String resourceName) { return [resNameObj2].get(resourceName).intValue(); } ... public int get[ResNameObjN](String resourceName) { return [resNameObjN].get(resourceName).intValue(); } } The question is: Will I add too much memory use of the device? Is it worth it? Regards,

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  • Who calls the Destructor of the class when operator delete is used in multiple inheritance.

    - by dicaprio-leonard
    This question may sound too silly, however , I don't find concrete answer any where else. With little knowledge on how late binding works and virtual keyword used in inheritance. As in the code sample, when in case of inheritance where a base class pointer pointing to a derived class object created on heap and delete operator is used to deallocate the memory , the destructor of the of the derived and base will be called in order only when the base destructor is declared virtual function. Now my question is : 1) When the destructor of base is not virtual, why the problem of not calling derived dtor occur only when in case of using "delete" operator , why not in the case given below: derived drvd; base *bPtr; bPtr = &drvd; //DTOR called in proper order when goes out of scope. 2) When "delete" operator is used, who is reponsible to call the destructor of the class? The operator delete will have an implementation to call the DTOR ? or complier writes some extra stuff ? If the operator has the implementation then how does it looks like , [I need sample code how this would have been implemented]. 3) If virtual keyword is used in this example, how does operator delete now know which DTOR to call? Fundamentaly i want to know who calls the dtor of the class when delete is used. Sample Code class base { public: base() { cout<<"Base CTOR called"<<endl; } virtual ~base() { cout<<"Base DTOR called"<<endl; } }; class derived:public base { public: derived() { cout<<"Derived CTOR called"<<endl; } ~derived() { cout<<"Derived DTOR called"<<endl; } }; I'm not sure if this is a duplicate, I couldn't find in search. int main() { base *bPtr = new derived(); delete bPtr;// only when you explicitly try to delete an object return 0; }

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  • Function Point Analysis -- a seriously overestimating technique?

    - by kizzx2
    I know questions about FPA has been asked numerous times before, but this time I'm taking a more analytical angle at it, backed up with data. 1. First, some data This question is based on a tutorial. He had a "Sample Count" section where he demonstrated it step by step. You can see some screenshots of his sample application here. In the end, he calculated the unadjusted FP to be 99. There is another article on InformIT with industry data on typical hour/FP. It ranges from 2 hours/FP to 27.4 hours/FP. Let's try to stick with 2 for the moment (since SO readers are probably the more efficient crowd :p). 2. Reality check!? Now just check out the screenshots again. Do a little math here 99 * 2 = 198 hours 198 hours / 40 hours per week = 5 weeks Seriously? That sample application is going to take 5 weeks to implement? Is it just my feeling that it wouldn't take any decent programmer longer than one week (I"m not even saying weekend) to have it completed? Now let's try estimating the cost of the project. We'll use New York's minimum wage at the moment (Wikipedia), which is $7.25 198 * 7.25 = $1435.5 From what I could see from the screenshots, this application is a small excel-improvement app. I could have bought MS Office Pro for 200 bucks which gives me greater interoperability (.xls files) and flexibility (spreadsheets). (For the record, that same Web site has another article discussing productivity. It seems like they typically use 4.2 hours/FP, which gives us even more shocking stats: 99 * 4.2 = 415 hours = 10 weeks = almost 3 whopping months! 415 hours * $7.25 = $3000 zomg (That's even assuming that all our poor coders get the minimum wage!) 3. Am I missing something here? Right now, I could come up with several possible explanation: FPA is really only suited for bigger projects (1000+ FPs) so it becomes extremely inaccurate at smaller scale. The hours/FP metric fluctuates abruptly from team to team, project to project. For a small project like this, we could have used something like 0.5 hour/FP or something. (Now this kind of makes the whole estimation thing pointless, unless my firm does the same type of projects for several years with the same team, not really common.) From my experience with several software metrics, Function Point is really not a lightweight metric. If the hour/FP thing fluctuates so much, then what's the point, maybe I could have gone with User Story Points which is a lot faster to get and arguably almost as uncertain. What would be the FP experts' answers to this?

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  • Increase efficiency for an R simulator of the Monty Hall Puzzle

    - by jahan_m
    The Monty Hall Problem is a simple puzzle involving probability that even stumps professionals in careers dealing with some heavy-duty math. Here's the basic problem: Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice? You can find numerous explanations of the solution here: http://en.wikipedia.org/wiki/Monty_Hall_problem Goal of my simulation: Prove that a switching strategy will win you the car 2/3 of the time. I got curious and wanted to write a little function that simulates the problem many times and returns the proportion of wins if you switched and the proportion of wins if you stayed with your first choice. The function then plots the cumulative wins. First and foremost, I'm interested in hearing if my simulation is indeed replicating the Monty Problem, or if some aspect of the code got it wrong. Secondly, this function takes a long time to run once I get to about 10,000 simulations. I know I don't need this many simulations to prove this but I'd love to hear some ideas on how to make it more efficient. Thanks for your feedback! Monty_Hall=function(repetitions){ doors=c('A','B','C') stay_wins=0 switch_wins=0 series=data.frame(sim_num=seq(repetitions),cum_sum_stay=replicate(repetitions,0),cum_sum_switch=replicate(repetitions,0)) for(i in seq(repetitions)){ winning_door=sample(doors,1) contestant_chooses=sample(doors,1) if(contestant_chooses==winning_door) stay_wins=stay_wins+1 else switch_wins=switch_wins+1 series[i,'cum_sum_stay']=stay_wins series[i,'cum_sum_switch']=switch_wins } plot(series$sim_num,series$cum_sum_switch,col=2,ylab='Cumulative # of wins', xlab='Simulation #',main=sprintf('%d Simulations of the Monty Hall Paradox',repetitions),type='l') lines(series$sim_num,series$cum_sum_stay,col=4) legend('topleft',legend=c('Cumulative wins from switching', 'Cumulative wins from staying'),col=c(2,4),lty=1) result=list(series=series,stay_wins=stay_wins,switch_wins=switch_wins, proportion_stay_wins=stay_wins/repetitions, proportion_switch_wins=switch_wins/repetitions) return(result) } #Theory predicts that it is to the contestant's advantage if he #switches his choice to the other door. This function simulates the game #many times, and shows you the proportion of games in which staying or #switching would win the car. It also plots the cumulative wins for each strategy. Monty_Hall(100)

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  • iPhone RSS thumbnail

    I have a simple RSS reader. Stories are downloaded, put into a UITableView, and when you click it, each story loads in a UIWebView. It works great. Now though, I'd like to incorporate an image on the left side (like you'd see in the YouTube app). However, since my app pulls from an RSS feed, I can't simply specify image X to appear in row X because row X will be row Y tomorrow, and things will get out of order, you know? I am currently pulling from a YouTube RSS feed, and can get the video title, description, publication date, but I'm stuck as to how to pull the little thumbnail besides each entry in the feed. As you can probably tell, I'm a coding newbie (this being my first application other than a Hello World app) and I'm getting so frustrated by my own lack of knowledge. Thanks! BTW, here's some sample code: - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{ //NSLog(@"found this element: %@", elementName); if (currentElement) { [currentElement release]; currentElement = nil; } currentElement = [elementName copy]; if ([elementName isEqualToString:@"item"]) { // clear out our story item caches... item = [[NSMutableDictionary alloc] init]; currentTitle = [[NSMutableString alloc] init]; currentDate = [[NSMutableString alloc] init]; currentSummary = [[NSMutableString alloc] init]; currentLink = [[NSMutableString alloc] init]; } } - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{ //NSLog(@"ended element: %@", elementName); if ([elementName isEqualToString:@"item"]) { // save values to an item, then store that item into the array... [item setObject:currentTitle forKey:@"title"]; [item setObject:currentLink forKey:@"link"]; [item setObject:currentSummary forKey:@"summary"]; [item setObject:currentDate forKey:@"date"]; [stories addObject:[item copy]]; NSLog(@"adding story: %@", currentTitle); } } - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{ //NSLog(@"found characters: %@", string); // save the characters for the current item... if ([currentElement isEqualToString:@"title"]) { [currentTitle appendString:string]; } else if ([currentElement isEqualToString:@"link"]) { [currentLink appendString:string]; } else if ([currentElement isEqualToString:@"description"]) { [currentSummary appendString:string]; } else if ([currentElement isEqualToString:@"pubDate"]) { [currentDate appendString:string]; } }

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  • Unable to install gem "pg" on Ubuntu 12.10 (AMD64)

    - by Lynx_Eyes
    I've been (unsuccessfully) trying to install the "pg" gem on my ruby 1.9.3-p286 but nothing seems to work. I've already installed postgresql (9.1), libpq-dev and a few others like postgresql-server-dev-9.1. I've tried to pass the "with-pg-config" flag to the gem install but simply nothing seems to work. Every time I try to install the gem it outputs something like this: Building native extensions. This could take a while... ERROR: Error installing pg: ERROR: Failed to build gem native extension. /home/lynux/.rvm/rubies/ruby-1.9.3-p286/bin/ruby extconf.rb checking for pg_config... yes Using config values from /usr/bin/pg_config checking for libpq-fe.h... yes checking for libpq/libpq-fs.h... yes checking for pg_config_manual.h... yes checking for PQconnectdb() in -lpq... no checking for PQconnectdb() in -llibpq... no checking for PQconnectdb() in -lms/libpq... no Can't find the PostgreSQL client library (libpq) *** extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/home/lynux/.rvm/rubies/ruby-1.9.3-p286/bin/ruby --with-pg --without-pg --with-pg-dir --without-pg-dir --with-pg-include --without-pg-include=${pg-dir}/include --with-pg-lib --without-pg-lib=${pg-dir}/lib --with-pg-config --without-pg-config --with-pg_config --without-pg_config --with-pqlib --without-pqlib --with-libpqlib --without-libpqlib --with-ms/libpqlib --without-ms/libpqlib Gem files will remain installed in /home/lynux/.rvm/gems/ruby-1.9.3-p286@phisiodata/gems/pg-0.14.1 for inspection. Results logged to /home/lynux/.rvm/gems/ruby-1.9.3-p286@phisiodata/gems/pg-0.14.1/ext/gem_make.out What am I doing wrong? Is there something else that I should do before trying to install the gem? Thank you in advance. [EDIT] Ok, so joelparkerhenderson's answer set me to think that there might me something wrong with paths and libraries and a went on digging a little bit further.. I've found this awesome post and it solved! Basically the problem lies with RVM. So, my problem is solved and for anyone out there that might suffer from the same thing, follow the link!

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  • Overwhelmed by design patterns... where to begin?

    - by Pete
    I am writing a simple prototype code to demonstrate & profile I/O schemes (HDF4, HDF5, HDF5 using parallel IO, NetCDF, etc.) for a physics code. Since focus is on IO, the rest of the program is very simple: class Grid { public: floatArray x,y,z; }; class MyModel { public: MyModel(const int &nip1, const int &njp1, const int &nkp1, const int &numProcs); Grid grid; map<string, floatArray> plasmaVariables; }; Where floatArray is a simple class that lets me define arbitrary dimensioned arrays and do mathematical operations on them (i.e. x+y is point-wise addition). Of course, I could use better encapsulation (write accessors/setters, etc.), but that's not the concept I'm struggling with. For the I/O routines, I am envisioning applying simple inheritance: Abstract I/O class defines read & write functions to fill in the "myModel" object HDF4 derived class HDF5 HDF5 using parallel IO NetCDF etc... The code should read data in any of these formats, then write out to any of these formats. In the past, I would add an AbstractIO member to myModel and create/destroy this object depending on which I/O scheme I want. In this way, I could do something like: myModelObj.ioObj->read('input.hdf') myModelObj.ioObj->write('output.hdf') I have a bit of OOP experience but very little on the Design Patterns front, so I recently acquired the Gang of Four book "Design Patterns: Elements of Reusable Object-Oriented Software". OOP designers: Which pattern(s) would you recommend I use to integrate I/O with the myModel object? I am interested in answering this for two reasons: To learn more about design patterns in general Apply what I learn to help refactor an large old crufty/legacy physics code to be more human-readable & extensible. I am leaning towards applying the Decerator pattern to myModel, so I can attach the I/O responsibilities dynamically to myModel (i.e. whether to use HDF4, HDF5, etc.). However, I don't feel very confident that this is the best pattern to apply. Reading the Gang of Four book cover-to-cover before I start coding feels like a good way to develop an unhealthy caffeine addiction. What patterns do you recommend?

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  • Ajax success function firing before java class responds

    - by user1899281
    I am creating a login function with ajax and am having an issue where the success function (SuccessLogin) fires before getting an ajax response. I am running the code as google web app from eclipse and I can see when debugging the java class file, that the javascript is throwing an alert for the success response from the class being false before the debugger catches the break point in the class file. I have only been writing code for a couple months now so I am sure its a stupid little error on my part. $(document).ready(function() { sessionChecker() // sign in $('#signInForm').click(function () { $().button('loading') var email = $('#user_username').val(); sessionStorage.email = $('#user_username').val(); var password= $('#user_password').val(); var SignInRequest = { type: "UserLoginRequest", email: email, password: password } var data= JSON.stringify(SignInRequest); //disabled all the text fields $('.text').attr('disabled','true'); //start the ajax $.ajax({ url: "/resources/user/login", type: "POST", data: data, cache: false, success: successLogin(data) }); }); //if submit button is clicked $('#Register').click(function () { $().button('loading') var email = $('#email').val(); if ($('#InputPassword').val()== $('#ConfirmPassword').val()) { var password= $('input[id=InputPassword]').val(); } else {alert("Passwords do not match"); return ;} var UserRegistrationRequest = { type: "UserRegistrationRequest", email: email, password: password } var data= JSON.stringify(UserRegistrationRequest); //disabled all the text fields $('.text').attr('disabled','true'); //start the ajax $.ajax({ url: "/resources/user/register", type: "POST", data: data, cache: false, success: function (data) { if (data.success==true) { //hide the form $('form').fadeOut('slow'); //show the success message $('.done').fadeIn('slow'); } else alert('data.errorReason'); } }); return false; }); }); function successLogin (data){ if (data.success) { sessionStorage.userID= data.userID var userID = data.userID sessionChecker(userID); } else alert(data.errorReason); } //session check function sessionChecker(uid) { if (sessionStorage.userID!= null){ var userID = sessionStorage.userID }; if (userID != null){ $('#user').append(userID) $('#fat-menu_1').fadeOut('slow') $('#fat-menu_2').append(sessionStorage.email).fadeIn('slow') }; }

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  • wxpython - Nested Notebooks

    - by madtowneast
    I have been trying to make my nested notebooks a little bit more appealing code wise. At the moment, I got this #!/usr/bin/env python import os import sys import datetime import numpy as np from readmonifile import MonitorFile from sortmonifile import sort import wx class NestedPanelOne(wx.Panel): #---------------------------------------------------------------------- # First notebook that creates the tab to select the component number #---------------------------------------------------------------------- def __init__(self, parent, label, data): wx.Panel.__init__(self, parent=parent, id=wx.ID_ANY) sizer = wx.BoxSizer(wx.VERTICAL) #Loop creating the tabs according to the component name nestedNotebook = wx.Notebook(self, wx.ID_ANY) for slabel in sorted(data[label].keys()): tab = NestedPanelTwo(nestedNotebook, label, slabel, data) nestedNotebook.AddPage(tab,slabel) sizer = wx.BoxSizer(wx.VERTICAL) sizer.Add(nestedNotebook, 1, wx.ALL|wx.EXPAND, 5) self.SetSizer(sizer) class NestedPanelTwo(wx.Panel): #------------------------------------------------------------------------------ # Second notebook that creates the tab to select the main monitoring variables #------------------------------------------------------------------------------ def __init__(self, parent, label, slabel, data): wx.Panel.__init__(self, parent=parent, id=wx.ID_ANY) sizer = wx.BoxSizer(wx.VERTICAL) nestedNotebook = wx.Notebook(self, wx.ID_ANY) for sslabel in sorted(data[label][slabel][data[label][slabel].keys()[0]].keys()): tab = NestedPanelThree(nestedNotebook, label, slabel, sslabel, data) nestedNotebook.AddPage(tab, sslabel) sizer.Add(nestedNotebook, 1, wx.ALL|wx.EXPAND, 5) self.SetSizer(sizer) class NestedPanelThree(wx.Panel): #------------------------------------------------------------------------------- # Third notebook that creates checkboxes to select the monitoring sub-variables #------------------------------------------------------------------------------- def __init__(self, parent, label, slabel, sslabel, data): wx.Panel.__init__(self, parent=parent, id=wx.ID_ANY) labels=[] chbox =[] chboxdict={} for ssslabel in sorted(data[label][slabel][data[label][slabel].keys()[0]][sslabel].keys()): labels.append(ssslabel) for item in list(set(labels)): cb = wx.CheckBox(self, -1, item) chbox.append(cb) chboxdict[item]=cb gridSizer = wx.GridSizer(np.shape(list(set(labels)))[0],3, 5, 5) gridSizer.AddMany(chbox) self.SetSizer(gridSizer) ######################################################################## class NestedNotebookDemo(wx.Notebook): #--------------------------------------------------------------------------------- # Main notebook creating tabs for the monitored components #--------------------------------------------------------------------------------- def __init__(self, parent, data): wx.Notebook.__init__(self, parent, id=wx.ID_ANY, style= wx.BK_DEFAULT ) for label in sorted(data.keys()): print label tab = NestedPanelOne(self,label, data) self.AddPage(tab, label) ######################################################################## class DemoFrame(wx.Frame): #---------------------------------------------------------------------- # Putting it all together #---------------------------------------------------------------------- def __init__(self,data): wx.Frame.__init__(self, None, wx.ID_ANY, "pDAQ monitoring plotting tool", size=(800,400) ) panel = wx.Panel(self) notebook = NestedNotebookDemo(panel, data) sizer = wx.BoxSizer(wx.VERTICAL) sizer.Add(notebook, 1, wx.ALL|wx.EXPAND, 5) panel.SetSizer(sizer) self.Layout() #Menu Bar to be added later ''' menubar = wx.MenuBar() file = wx.Menu() file.Append(1, '&Quit', 'Exit Tool') menubar.Append(file, '&File') self.SetMenuBar(menubar) self.Bind(wx.EVT_MENU, self.OnClose, id=1) ''' self.Show() #---------------------------------------------------------------------- if __name__ == "__main__": if len(sys.argv) == 1: raise SystemExit("Please specify a file to process") for f in sys.argv[1:]: data=sort.sorting(f) print data['stringHub'].keys() print data.keys() print data[data.keys()[0]].keys() print 'test' app = wx.PySimpleApp() frame = DemoFrame(data) app.MainLoop() print 'testend' and I would like to reduce this whole mess into something that only has three nested for loops, so something like for label in sorted(data.keys()): self.SubNoteBooks[label] = wx.Notebook(self.Notebook, wx.ID_ANY) self.Notebook.AddPage(self.SubNoteBooks[label], label) for slabel in sorted(data[label].keys()): self.SubNoteBooks[label][slabel] = wx.Notebook(self, wx.ID_ANY) self.SubNoteBooks[label].AddPage(self.SubNoteBooks[label][slabel], slabel) for sslabel in sorted(data[label][slabel][data[label][slabel].keys()[0]].keys()): self.SubNoteBooks[label][slabel][sslabel] = wx.Notebook(self.Notebook, wx.ID_ANY) self.Notebook.AddPage(self.SubNoteBooks[label][slabel][sslabel], sslabel) I have been trying to fiddle this around but the problem seems to be the line self.SubNoteBooks[label][slabel] = wx.Notebook(self, wx.ID_ANY) I get the error: Traceback (most recent call last): File "./reducelinenumbers.py", line 162, in <module> frame = DemoFrame(data) File "./reducelinenumbers.py", line 126, in __init__ self.SubNoteBooks[label][slabel] = wx.Notebook(self, wx.ID_ANY) TypeError: 'Notebook' object does not support item assignment I understand why notebook is being type raises a TypeError here. Is there a way around this? Thanks a bunch in advance.

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  • Interoperability between two AES algorithms

    - by lpfavreau
    Hello, I'm new to cryptography and I'm building some test applications to try and understand the basics of it. I'm not trying to build the algorithms from scratch but I'm trying to make two different AES-256 implementation talk to each other. I've got a database that was populated with this Javascript implementation stored in Base64. Now, I'm trying to get an Objective-C method to decrypt its content but I'm a little lost as to where the differences in the implementations are. I'm able to encrypt/decrypt in Javascript and I'm able to encrypt/decrypt in Cocoa but cannot make a string encrypted in Javascript decrypted in Cocoa or vice-versa. I'm guessing it's related to the initialization vector, nonce, counter mode of operation or all of these, which quite frankly, doesn't speak to me at the moment. Here's what I'm using in Objective-C, adapted mainly from this and this: @implementation NSString (Crypto) - (NSString *)encryptAES256:(NSString *)key { NSData *input = [self dataUsingEncoding: NSUTF8StringEncoding]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:TRUE]; return [Base64 encode:output]; } - (NSString *)decryptAES256:(NSString *)key { NSData *input = [Base64 decode:self]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:FALSE]; return [[[NSString alloc] initWithData:output encoding:NSUTF8StringEncoding] autorelease]; } + (NSData *)cryptoAES256:(NSData *)input key:(NSString *)key doEncrypt:(BOOL)doEncrypt { // 'key' should be 32 bytes for AES256, will be null-padded otherwise char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused) bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding) // fetch key data [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [input length]; // See the doc: For block ciphers, the output size will always be less than or // equal to the input size plus the size of one block. // That's why we need to add the size of one block here size_t bufferSize = dataLength + kCCBlockSizeAES128; void* buffer = malloc(bufferSize); size_t numBytesCrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(doEncrypt ? kCCEncrypt : kCCDecrypt, kCCAlgorithmAES128, kCCOptionECBMode | kCCOptionPKCS7Padding, keyPtr, kCCKeySizeAES256, nil, // initialization vector (optional) [input bytes], dataLength, // input buffer, bufferSize, // output &numBytesCrypted ); if (cryptStatus == kCCSuccess) { // the returned NSData takes ownership of the buffer and will free it on deallocation return [NSData dataWithBytesNoCopy:buffer length:numBytesCrypted]; } free(buffer); // free the buffer; return nil; } @end Of course, the input is Base64 decoded beforehand. I see that each encryption with the same key and same content in Javascript gives a different encrypted string, which is not the case with the Objective-C implementation that always give the same encrypted string. I've read the answers of this post and it makes me believe I'm right about something along the lines of vector initialization but I'd need your help to pinpoint what's going on exactly. Thank you!

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  • Any socket programmers out there? How can I obtain the IPv4 address of the client?

    - by Dr Dork
    Hello! I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code setup to listen for incoming TCP connection requests from clients after the parent socket has been created and is set to listen... int sockfd, newfd; unsigned int len; socklen_t sin_size; char msg[]="Test message sent"; char buf[MAXLEN]; int st, rv; struct addrinfo hints, *serverinfo, *p; struct sockaddr_storage client; char ip[INET6_ADDRSTRLEN]; . . //parent socket creation and listen code omitted for simplicity . //wait for connection requests from clients while(1) { //Returns the socketID and address of client connecting to socket if( ( newfd = accept(sockfd, (struct sockaddr *)&client, &len) ) == -1 ){ perror("Accept"); exit(-1); } if( (rv = recv(newfd, buf, MAXLEN-1, 0 )) == -1) { perror("Recv"); exit(-1); } struct sockaddr_in *clientAddr = ( struct sockaddr_in *) get_in_addr((struct sockaddr *)&client); inet_ntop(client.ss_family, clientAddr, ip, sizeof ip); printf("Receive from %s: query type is %s\n", ip, buf); if( ( st = send(newfd, msg, strlen(msg), 0)) == -1 ) { perror("Send"); exit(-1); } //ntohs is used to avoid big-endian and little endian compatibility issues printf("Send %d byte to port %d\n", ntohs(clientAddr->sin_port) ); close(newfd); } } I found the get_in_addr function online and placed it at the top of my code and use it to obtain the IP address of the client connecting... // get sockaddr, IPv4 or IPv6: void *get_in_addr(struct sockaddr *sa) { if (sa->sa_family == AF_INET) { return &(((struct sockaddr_in*)sa)->sin_addr); } return &(((struct sockaddr_in6*)sa)->sin6_addr); } but the function always returns the IPv6 IP address since thats what the sa_family property is set as. My question is, is the IPv4 IP address stored anywhere in the data I'm using and, if so, how can I access it? Thanks so much in advance for all your help!

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  • jQuery fadeIn fadeOut pause on hover

    - by theDawckta
    I have a little jQuery snippet that will fadeIn and fadeOut a group of divs over a select interval. I now need to pause this fadeIn fadeOut on hover, then resume on mouse out. Any help is appreciated. Here is the relevant code. The following is what is located in my body <div class="gcRotate"> <div class="gcRotateContent"> <div style="border: solid 2px black; text-align: center; width: 150px;"> This is first content <img src="http://pix.motivatedphotos.com/2008/6/16/633492359109161542-Skills.jpg" alt="Dude" /> </div> </div> <div class="gcRotateContent"> <div style="border: solid 2px black; text-align: center; width: 150px"> This is second content <img src="http://www.funnycorner.net/funny-pictures/5010/cheezburger-locats.jpg" alt="Dude" /> </div> </div> <div class="gcRotateContent"> <div style="border: solid 2px black; text-align: center; width: 150px"> This is third content <img src="http://icanhascheezburger.files.wordpress.com/2007/06/business.jpg" alt="Dude" /> </div> </div> </div> <div> This shouldn't move. </div> <script type="text/javascript"> function fadeContent() { $(".gcRotate .gcRotateContent:hidden:first").fadeIn(500).delay(2000).fadeOut(500, function() { $(this).appendTo($(this).parent()); fadeContent(); }); } $(".gcRotate").height(0); $(".gcRotateContent").each( function() { if ($(".gcRotate").height() < $(this).height()) { $(".gcRotate").height($(this).height()); } } ); $(".gcRotateContent").each(function() { $(this).css("display", "none") }); fadeContent(); </script>

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  • Using PHP session_id() to Make Sure iframe is Generated by Our Server Dynamically

    - by Michael Robinson
    We use iframes to show ads on our site. Iframes are used to allow us to keep the ad generation code and other site modules separate. As we track ad views on our site, and need to be able to keep an accurate count of which pagetype gets what views, I must ensure that users can't simply copy-paste the iframe in which the ad is loaded onto another site. This would cause ad count to become inflated for this page, and the count would not match the view count of the page the iframe "should" be displayed in. Before anyone says so: no I can't simply compare the page view count with the ad view count, or use the page view count * number of ads per page, as # of ads per page will not necessarily be static. I need to come up with a solution that will allow ads to be shown only for iframes that are generated dynamically and are shown on our pages. I am not familiar with PHP sessions, but from what little reading I have had time to do, the following seems to be to be an acceptable solution: Add "s = session_id()" to the src of the ad's iframe. In the code that receives and processes ad requests, only return (and count) and ad if s == session_id(). Please correct me if I'm wrong, but this would ensure: Ads would only be returned to iframes whose src was generated alongside the rest of the page's content, as is the case during normal use. We can return our logo to ad calls with an invalid session_id. So a simple example would be: One of our pages: <?php session_start(); ?> <div id="someElement"> <!-- EVERYONE LOVES ADS --> <iframe src="http//awesomesite.com/ad/can_has_ad.php?s=<?php echo session_id(); ?>></iframe> </div> ad/can_has_ad.php: <?php session_start(); ?> if($_GET['s'] == session_id()){ echo 'can has ad'; } else{ echo '<img src="http://awesomesite.com/images/canhaslogo.jpg"/>'; } And finally, copied code with static 's' parameter: <!-- HAHA LULZ I WILL SCREW WITH YOUR AD VIEW COUNTS LULZ HAHA --> <iframe src="http//awesomesite.com/ad/can_has_ad.php?s=77f2b5fcdab52f52607888746969b0ad></iframe> Which would give them an iframe showing our awesome site's logo, and not screw with our view counts. I made some basic test cases: two files, one that generates the iframe and echos it, and one that the iframe's src is pointed to, that checks the 's' parameter and shows an appropriate message depending on the result. I copied the iframe into a file and hosted it on a different server, and the correct message was displayed (cannot has ad). So, my question is: Would this work or am I being a PHP session noob, with the above test being a total fluke? Thanks for your time! Edit: I'm trying to solve this without touching the SQL server

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  • How Do I Prevent Rails From Treating Edit Fields_For Differently From New Fields_For

    - by James
    I am using rails3 beta3 and couchdb via couchrest. I am not using active record. I want to add multiple "Sections" to a "Guide" and add and remove sections dynamically via a little javascript. I have looked at all the screencasts by Ryan Bates and they have helped immensely. The only difference is that I want to save all the sections as an array of sections instead of individual sections. Basically like this: "sections" => [{"title" => "Foo1", "content" => "Bar1"}, {"title" => "Foo2", "content" => "Bar2"}] So, basically I need the params hash to look like that when the form is submitted. When I create my form I am doing the following: <%= form_for @guide, :url => { :action => "create" } do |f| %> <%= render :partial => 'section', :collection => @guide.sections %> <%= f.submit "Save" %> <% end %> And my section partial looks like this: <%= fields_for "sections[]", section do |guide_section_form| %> <%= guide_section_form.text_field :section_title %> <%= guide_section_form.text_area :content, :rows => 3 %> <% end %> Ok, so when I create the guide with sections, it is working perfectly as I would like. The params hash is giving me a sections array just like I would want. The problem comes when I want edit guide/sections and save them again because rails is inserting the id of the guide in the id and name of each form field, which is screwing up the params hash on form submission. Just to be clear, here is the raw form output for a new resource: <input type="text" size="30" name="sections[][section_title]" id="sections__section_title"> <textarea rows="3" name="sections[][content]" id="sections__content" cols="40"></textarea> And here is what it looks like when editing an existing resource: <input type="text" value="Foo1" size="30" name="sections[cd2f2759895b5ae6cb7946def0b321f1][section_title]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_section_title"> <textarea rows="3" name="sections[cd2f2759895b5ae6cb7946def0b321f1][content]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_content" cols="40">Bar1</textarea> How do I force rails to always use the new resource behavior and not automatically add the id to the name and value. Do I have to create a custom form builder? Is there some other trick I can do to prevent rails from putting the id of the guide in there? I have tried a bunch of stuff and nothing is working. Thanks in advance!

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  • How to transform a cached XML via XSL?

    - by TruMan1
    I have a PHP script that caches a remote XML file. I want to XSL transform it before caching, but don't know how to do this: <?php // Set this to your link Id $linkId = "0oiy8Plr697u3puyJy9VTUWfPrCEvEgJR"; // Set this to a directory that has write permissions // for this script $cacheDir = "temp/"; $cachetime = 15 * 60; // 15 minutes // Do not change anything below this line // unless you are absolutely sure $feedUrl="http://mydomain.com/messageService/guestlinkservlet?glId="; $cachefile = $cacheDir .$linkId.".xml"; header('Content-type: text/xml'); // Send from the cache if $cachetime is not exceeded if (file_exists($cachefile) && (time() - $cachetime < filemtime($cachefile))) { include($cachefile); echo "<!-- Cached ".date('jS F Y H:i', filemtime($cachefile))." -->\n"; exit; } $contents = file_get_contents($feedUrl . $linkId); // show the contents of the XML file echo $contents; // write it to the cache $fp = fopen($cachefile, 'w'); fwrite($fp, $contents); fclose($fp); ?> This is the XSL string I want to use to transform it: <xsl:template match="/"> <kml xmlns="http://www.opengis.net/kml/2.2"> <Document> <xsl:apply-templates select="messageList" /> </Document> </kml> </xsl:template> <xsl:template match="messageList"> <name>My Generated KML</name> <xsl:apply-templates select="message" /> </xsl:template> <xsl:template match="message"> <Placemark> <name><xsl:value-of select="esnName" /></name> <Point> <coordinates> <xsl:value-of select="latitude" />,<xsl:value-of select="longitude" /> </coordinates> </Point> </Placemark> </xsl:template> I want to actually transform XML input and save/return a KML format. Can someone please help adjust this script? This was given to me and I am a little new to it.

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  • WPF Binding when setting DataTemplate Programically

    - by Daniel
    Hello, I have my little designer tool (my program). On the left side I have TreeView and on the right site I have Accordion. When I select a node I want to dynamically build Accordion Items based on Properties from DataContext of selected node. Selecting nodes works fine, and when I use this sample code for testing it works also. XAML code: <layoutToolkit:Accordion x:Name="accPanel" SelectionMode="ZeroOrMore" SelectionSequence="Simultaneous"> <layoutToolkit:AccordionItem Header="Controller Info"> <StackPanel Orientation="Horizontal" DataContext="{Binding}"> <TextBlock Text="Content:" /> <TextBlock Text="{Binding Path=Name}" /> </StackPanel> </layoutToolkit:AccordionItem> </layoutToolkit:Accordion> C# code: private void treeSceneNode_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e) { if (e.NewValue != e.OldValue) { if (e.NewValue is SceneNode) { accPanel.DataContext = e.NewValue; //e.NewValue is a class that contains Name property } } } But the problem occurs when I'm trying to achive this using DateTemplate and dynamically build AccordingItem, the Binding is not working: <layoutToolkit:Accordion x:Name="accPanel" SelectionMode="ZeroOrMore" SelectionSequence="Simultaneous"> </layoutToolkit:Accordion> and DateTemplate in my ResourceDictionary <DataTemplate x:Key="dtSceneNodeContent"> <StackPanel Orientation="Horizontal" DataContext="{Binding}"> <TextBlock Text="Content:" /> <TextBlock Text="{Binding Path=Name}" /> </StackPanel> </DataTemplate> and C# code: private void treeSceneNode_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e) { if (e.NewValue != e.OldValue) { ResourceDictionary rd = new ResourceDictionary(); rd.Source = new Uri("/SilverGL.GUI;component/SilverGLDesignerResourceDictionary.xaml", UriKind.RelativeOrAbsolute); if (e.NewValue is SceneNode) { accPanel.DataContext = e.NewValue; AccordionItem accController = new AccordionItem(); accController.Header = "Controller Info"; accController.ContentTemplate = rd["dtSceneNodeContent"] as DataTemplate; accPanel.Items.Add(accController); } else { // Other type of node } } } I really need help with this issue. Thanks for any support. Daniel

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  • Can this be imporved? Scrubing of dangerous html tags.

    - by chobo2
    Hi I been finding that for something that I consider pretty import there is very little information or libraries on how to deal with this problem. I found this while searching. I really don't know all the million ways that a hacker could try to insert the dangerous tags. I have a rich html editor so I need to keep non dangerous tags but strip out bad ones. So is this script missing anything? It uses html agility pack. public string ScrubHTML(string html) { HtmlDocument doc = new HtmlDocument(); doc.LoadHtml(html); //Remove potentially harmful elements HtmlNodeCollection nc = doc.DocumentNode.SelectNodes("//script|//link|//iframe|//frameset|//frame|//applet|//object|//embed"); if (nc != null) { foreach (HtmlNode node in nc) { node.ParentNode.RemoveChild(node, false); } } //remove hrefs to java/j/vbscript URLs nc = doc.DocumentNode.SelectNodes("//a[starts-with(translate(@href, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'javascript')]|//a[starts-with(translate(@href, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'jscript')]|//a[starts-with(translate(@href, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'vbscript')]"); if (nc != null) { foreach (HtmlNode node in nc) { node.SetAttributeValue("href", "#"); } } //remove img with refs to java/j/vbscript URLs nc = doc.DocumentNode.SelectNodes("//img[starts-with(translate(@src, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'javascript')]|//img[starts-with(translate(@src, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'jscript')]|//img[starts-with(translate(@src, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'vbscript')]"); if (nc != null) { foreach (HtmlNode node in nc) { node.SetAttributeValue("src", "#"); } } //remove on<Event> handlers from all tags nc = doc.DocumentNode.SelectNodes("//*[@onclick or @onmouseover or @onfocus or @onblur or @onmouseout or @ondoubleclick or @onload or @onunload]"); if (nc != null) { foreach (HtmlNode node in nc) { node.Attributes.Remove("onFocus"); node.Attributes.Remove("onBlur"); node.Attributes.Remove("onClick"); node.Attributes.Remove("onMouseOver"); node.Attributes.Remove("onMouseOut"); node.Attributes.Remove("onDoubleClick"); node.Attributes.Remove("onLoad"); node.Attributes.Remove("onUnload"); } } // remove any style attributes that contain the word expression (IE evaluates this as script) nc = doc.DocumentNode.SelectNodes("//*[contains(translate(@style, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'expression')]"); if (nc != null) { foreach (HtmlNode node in nc) { node.Attributes.Remove("stYle"); } } return doc.DocumentNode.WriteTo(); }

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  • Moving a unit precisely along a path in x,y coordinates

    - by Adam Eberbach
    I am playing around with a strategy game where squads move around a map. Each turn a certain amount of movement is allocated to a squad and if the squad has a destination the points are applied each turn until the destination is reached. Actual distance is used so if a squad moves one position in the x or y direction it uses one point, but moving diagonally takes ~1.4 points. The squad maintains actual position as float which is then rounded to allow drawing the position on the map. The path is described by touching the squad and dragging to the end position then lifting the pen or finger. (I'm doing this on an iPhone now but Android/Qt/Windows Mobile would work the same) As the pointer moves x, y points are recorded so that the squad gains a list of intermediate destinations on the way to the final destination. I'm finding that the destinations are not evenly spaced but can be further apart depending on the speed of the pointer movement. Following the path is important because obstacles or terrain matter in this game. I'm not trying to remake Flight Control but that's a similar mechanic. Here's what I've been doing, but it just seems too complicated (pseudocode): getDestination() { - self.nextDestination = remove_from_array(destinations) - self.gradient = delta y to destination / delta x to destination - self.angle = atan(self.gradient) - self.cosAngle = cos(self.angle) - self.sinAngle = sin(self.angle) } move() { - get movement allocation for this turn - if self.nextDestination not valid - - getNextDestination() - while(nextDestination valid) && (movement allocation remains) { - - find xStep and yStep using movement allocation and sinAngle/cosAngle calculated for current self.nextDestination - - if current position + xStep crosses the destination - - - find x movement remaining after self.nextDestination reached - - - calculate remaining direct path movement allocation (xStep remaining / cosAngle) - - - make self.position equal to self.nextDestination - - else - - - apply xStep and yStep to current position - } - round squad's float coordinates to integer screen coordinates - draw squad image on map } That's simplified of course, stuff like sign needs to be tweaked to ensure movement is in the right direction. If trig is the best way to do it then lookup tables can be used or maybe it doesn't matter on modern devices like it used to. Suggestions for a better way to do it? an update - iPhone has zero issues with trig and tracking tens of positions and tracks implemented as described above and it draws in floats anyway. The Bresenham method is more efficient, trig is more precise. If I was to use integer Bresenham I would want to multiply by ten or so to maintain a little more positional accuracy to benefit collisions/terrain detection.

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  • PHP 'instanceof' failing with class constant

    - by Nathan Loding
    I'm working on a framework that I'm trying to type as strongly as I possibly can. (I'm working within PHP and taking some of the ideas that I like from C# and trying to utilize them within this framework.) I'm creating a Collection class that is a collection of domain entities/objects. It's kinda modeled after the List<T> object in .Net. I've run into an obstacle that is preventing me from typing this class. If I have a UserCollection, it should only allow User objects into it. If I have a PostCollection, it should only allow Post objects. All Collections in this framework need to have certain basic functions, such as add, remove, iterate. I created an interface, but found that I couldn't do the following: interface ICollection { public function add($obj) } class PostCollection implements ICollection { public function add(Post $obj) {} } This broke it's compliance with the interface. But I can't have the interface strongly typed because then all Collections are of the same type. So I attempted the following: interface ICollection { public function add($obj) } abstract class Collection implements ICollection { const type = 'null'; } class PostCollection { const type = 'Post'; public function add($obj) { if(!($obj instanceof self::type)) { throw new UhOhException(); } } } When I attempt to run this code, I get syntax error, unexpected T_STRING, expecting T_VARIABLE or '$' on the instanceof statement. A little research into the issue and it looks like the root of the cause is that $obj instanceof self is valid to test against the class. It appears that PHP doesn't process the entire self::type constant statement in the expression. Adding parentheses around the self::type variable threw an error regarding an unexpected '('. An obvious workaround is to not make the type variable a constant. The expression $obj instanceof $this->type works just fine (if $type is declared as a variable, of course). I'm hoping that there's a way to avoid that, as I'd like to define the value as a constant to avoid any possible change in the variable later. Any thoughts on how I can achieve this, or have I take PHP to it's limit in this regard? Is there a way of "escaping" or encapsulating self::this so that PHP won't die when processing it?

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  • General ORM design question

    - by Calvin
    Suppose you have 2 classes, Person and Rabbit. A person can do a number of things to a rabbit, s/he can either feed it, buy it and become its owner, or give it away. A rabbit can have none or at most 1 owner at a time. And if it is not fed for a while, it may die. Class Person { Void Feed(Rabbit r); Void Buy(Rabbit r); Void Giveaway(Person p, Rabbit r); Rabbit[] rabbits; } Class Rabbit { Bool IsAlive(); Person pwner; } There are a couple of observations from the domain model: Person and Rabbit can have references to each other Any actions on 1 object can also change the state of the other object Even if no explicit actions are invoked, there can still be a change of state in the objects (e.g. Rabbit can be starved to death, and that causes it to be removed from the Person.rabbits array) As DDD is concerned, I think the correct approach is to synchronize all calls that may change the states in the domain model. For instance, if a Person buys a Rabbit, s/he would need to acquire a lock in Person to make a change to the rabbits array AND also another lock in Rabbit to change its owner before releasing the first one. This would prevent a race condition where 2 Persons claim to be the owner of the little Rabbit. The other approach is to let the database to handle all these synchronizations. Who makes the first call wins, but then the DB needs to have some kind of business logics to figure out if it is a valid transaction (e.g. if a Rabbit already has an owner, it cannot change its owner unless the Person gives it away). There are both pros/cons in either approach, and I’d expect the “best” solution would be somewhere in-between. How would you do it in real life? What’s your take and experience? Also, is it a valid concern that there can be another race condition the domain model has committed its change but before it is fully committed in the database? And for the 3rd observation (i.e. state change due to time factor). How will you do it?

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  • Is this a valid pattern for raising events in C#?

    - by Will Vousden
    Update: For the benefit of anyone reading this, since .NET 4, the lock is unnecessary due to changes in synchronization of auto-generated events, so I just use this now: public static void Raise<T>(this EventHandler<T> handler, object sender, T e) where T : EventArgs { if (handler != null) { handlerCopy(sender, e); } } And to raise it: SomeEvent.Raise(this, new FooEventArgs()); Having been reading one of Jon Skeet's articles on multithreading, I've tried to encapsulate the approach he advocates to raising an event in an extension method like so (with a similar generic version): public static void Raise(this EventHandler handler, object @lock, object sender, EventArgs e) { EventHandler handlerCopy; lock (@lock) { handlerCopy = handler; } if (handlerCopy != null) { handlerCopy(sender, e); } } This can then be called like so: protected virtual void OnSomeEvent(EventArgs e) { this.someEvent.Raise(this.eventLock, this, e); } Are there any problems with doing this? Also, I'm a little confused about the necessity of the lock in the first place. As I understand it, the delegate is copied in the example in the article to avoid the possibility of it changing (and becoming null) between the null check and the delegate call. However, I was under the impression that access/assignment of this kind is atomic, so why is the lock necessary? Update: With regards to Mark Simpson's comment below, I threw together a test: static class Program { private static Action foo; private static Action bar; private static Action test; static void Main(string[] args) { foo = () => Console.WriteLine("Foo"); bar = () => Console.WriteLine("Bar"); test += foo; test += bar; test.Test(); Console.ReadKey(true); } public static void Test(this Action action) { action(); test -= foo; Console.WriteLine(); action(); } } This outputs: Foo Bar Foo Bar This illustrates that the delegate parameter to the method (action) does not mirror the argument that was passed into it (test), which is kind of expected, I guess. My question is will this affect the validity of the lock in the context of my Raise extension method? Update: Here is the code I'm now using. It's not quite as elegant as I'd have liked, but it seems to work: public static void Raise<T>(this object sender, ref EventHandler<T> handler, object eventLock, T e) where T : EventArgs { EventHandler<T> copy; lock (eventLock) { copy = handler; } if (copy != null) { copy(sender, e); } }

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  • How do I do high quality scaling of a image?

    - by pbhogan
    I'm writing some code to scale a 32 bit RGBA image in C/C++. I have written a few attempts that have been somewhat successful, but they're slow and most importantly the quality of the sized image is not acceptable. I compared the same image scaled by OpenGL (i.e. my video card) and my routine and it's miles apart in quality. I've Google Code Searched, scoured source trees of anything I thought would shed some light (SDL, Allegro, wxWidgets, CxImage, GD, ImageMagick, etc.) but usually their code is either convoluted and scattered all over the place or riddled with assembler and little or no comments. I've also read multiple articles on Wikipedia and elsewhere, and I'm just not finding a clear explanation of what I need. I understand the basic concepts of interpolation and sampling, but I'm struggling to get the algorithm right. I do NOT want to rely on an external library for one routine and have to convert to their image format and back. Besides, I'd like to know how to do it myself anyway. :) I have seen a similar question asked on stack overflow before, but it wasn't really answered in this way, but I'm hoping there's someone out there who can help nudge me in the right direction. Maybe point me to some articles or pseudo code... anything to help me learn and do. Here's what I'm looking for: 1. No assembler (I'm writing very portable code for multiple processor types). 2. No dependencies on external libraries. 3. I am primarily concerned with scaling DOWN, but will also need to write a scale up routine later. 4. Quality of the result and clarity of the algorithm is most important (I can optimize it later). My routine essentially takes the following form: DrawScaled( uint32 *src, uint32 *dst, src_x, src_y, src_w, src_h, dst_x, dst_y, dst_w, dst_h ); Thanks! UPDATE: To clarify, I need something more advanced than a box resample for downscaling which blurs the image too much. I suspect what I want is some kind of bicubic (or other) filter that is somewhat the reverse to a bicubic upscaling algorithm (i.e. each destination pixel is computed from all contributing source pixels combined with a weighting algorithm that keeps things sharp. EXAMPLE: Here's an example of what I'm getting from the wxWidgets BoxResample algorithm vs. what I want on a 256x256 bitmap scaled to 55x55. And finally: the original 256x256 image

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  • Audio/video streaming on Windows platform

    - by bushtucker
    I'm building an interactive language learning application to be used in a classroom environment. The idea is that a teacher should be able to talk to the students (=audio stream to all students), let students talk to each other (= audio P2P) in groups of two or more, let students watch a video coming from a the DVD player or coming from a media server. It should be possible to save the audio/video streams. The teacher should also be able to monitor, take-over or block the desktop of the students. The platform is Windows and it's a desktop application, no web application. The audio delay should be as minimal as poosible. Optionally a student sitting at home should be supported, but it's not a high priority. I am now finished with the classroom control part of the application (login, monitor, block, ...) and want to start the audio and video part. I've been evaluating several options like DirectX, GStreamer and SIP but now I have to make a decision. DirectX seems an obvious choice for the Windows platform, but it only lets me capture and playback audio and video. The encoding/decoding/network part I should do myself. GStreamer contains all kinds of options to capture/encode/stream/save audio and video streams. I've experimented a bit with it (ossbuild) and it does seem to involve a lot of trial and error to make something work: - microphone capture (via directsoundsrc) produces cracking noises on some computers - rtpL16 payloader didn't work well - streaming raw audio over the network only working at a sampling rate of 8000, no higher - there are a lot of errors when receiving mpeg4 video (bad I-frame), on some computers worse than others It is my impression that gstreamer is primary targetted at linux platforms. Development and support for the Windows platform seems to be a little behind. Nevertheless it's a powerful framework that could save me months and years of work. SIP seems to be able to do everything I want, but it is targeted towards telephony and IM. I don't know how flexible SIP is. It seems to me that the SIP layer would just be overhead as I already have a central (teacher) application that can control and setup all the streams. The interesting parts of frameworks like opalvoip and freeswitch are the actual audio/video capture, the encoding and transmission. Does anyone know how these interesting parts relate a framework like gstreamer? Are they easy to integrate into a custom application? Are they flexible enough? Does anyone have experience with all or one of these technologies? Maybe there are even other options I can look at? Many thanks for your advice

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  • getline() sets failbit and skips last line

    - by Thanatos
    I'm using std::getline() to enumerate through the lines in a file, and it's mostly working. It's left me curious however - std::getline() is skipping the very last line in my file, but only if it's blank. Using this minimal example: #include <iostream> #include <string> int main() { std::string line; while(std::getline(std::cin, line)) std::cout << "Line: “" << line << "”\n"; return 0; } If I feed it this: Line A Line B Line C I get those lines back at me. But this: Line A Line B Line C [* line is present but blank, ie, the file end is: "...B\nLine C\n" *] (I unfortunately can't have a blank line in SO's little code box thing...) So, first file has three lines ( ["Line A", "Line B", "Line C"] ), second file has four ( ["Line A", "Line B", "Line C", ""] ) This to me seems wrong - I have a four line file, and enumerating it with getline() leaves me with 3. What's really got me scratching my head is that this is exactly what the standard says it should do. (21.3.7.9) Even Python has similar behaviour (but it gives me the newlines too - C++ chops them off.) Is this some weird thing where C++ is expected lines to be terminated, and not separated by '\n', and I'm feeding it differently? Edit Clearly, I need to expand a bit here. I've met up with two philosophies of determining what a "line" in a file is: Lines are terminated by newlines - Dominant in systems such as Linux, and editors like vim. Possible to have a slightly "odd" file by not having a final '\n' (a "noeol" in vim). Impossible to have a blank line at the end of a file. Lines are separated by newlines - Dominant in just about every Windows editor I've ever come across. Every file is valid, and it's possible to have the last line be blank. Of course, YMMV as to what a newline is. I've always treated these as two completely different schools of thought. One earlier point I tried to make was to ask if the C++ standard was explicitly or merely implicitly following the first. (Curiously, where is Mac? terminated or separated?)

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